// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License.  You may obtain a copy of the License at

//

//   http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied.  See the License for the

// specific language governing permissions and limitations

// under the License.

#pragma once

#include <cstdint>

#include <utility>

#include "common/status.h"

namespace doris {

class AlgoUtil {

public:

    // descent the value step by step not linear continuity

    // If the result is linear continuity, then the value will changed very quickly and will cost

    // a lot of CPU and cache will not stable and will hold some lock.

    // Its better to use step num to be 10, do not use 3, the divide value is not stable.

    // For example, if step num is 3, then the result will be 0.33333... 0.66666..., the double value

    // is not stable.

    static double descent_by_step(int step_num, int64_t low_bound, int64_t high_bound,

                                  int64_t current) {

        if (current <= low_bound) {

            return 1;

        }

        if (current >= high_bound) {

            return 0;

        }

        if (high_bound <= low_bound) {

            // Invalid

            return 0;

        }

        // Use floor value, so that the step size is a little smaller than the actual value.

        // And then the used step will be a little larger than the actual value.

        int64_t step_size = (int64_t)std::floor((high_bound - low_bound) / (step_num * 1.0));

        int64_t used_step = (int64_t)std::ceil((current - low_bound) / (step_size * 1.0));

        // Then the left step is smaller than actual value.

        // This elimation algo will elimate more cache than actual.

        int64_t left_step = step_num - used_step;

        return left_step / (step_num * 1.0);

    }

};

} // namespace doris